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INA180: Response time in case of overload by offset

milordy COUTINHO
Prodigy 140 points
Part Number: INA180
Other Parts Discussed in Thread: INA181

Hello,
The ina180 for Vcm = 0 has offset +-150uv, let's suppose that I have -150uv offset, and that my shunt resistor is 0A, will I have an overload?
What would be the recovery time?
Figure 33 of the datasheet I imagine is wrong, probably that is from ina181.

  • 0
    TI__Mastermind 32395 points

    Hello milordy,

    Thanks for the question. Technically, once the offset (Vos) goes below 0V, then the input and output are being saturated with an inverting differential overload. 

    Figure 33 is vague, but the 0V origin should definitely apply to the red waveform (output). The input does look like it is going positive, but it should be that the source polarity was switched when driving the input. This is why it is called the Inverting Input in the legend. The true inverting overload response time begins once the input falls and the output settles to final value.

    Hope this makes sense.

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    Prodigy 140 points

    Would it have a higher resolution graphic?
    Does the response time depend on the magnitude of the negative voltage or not?
    Example:
    if it has -150uv (offset) and goes to + 10mv how long would it take?
    time would it really be -10mv?
    if you have -5mv and go to + 10mv how long would it take?

  • 0 in reply to milordy COUTINHO
    TI__Mastermind 32395 points

    Hey milordy,

    Yes the figure could use more resolution in order to see the response. Our apologies. The short answer is yes, the magnitude of the overdrive will affect the response time in many cases. Unfortunately, we do not have characterization data for this and device to device dissimilarities could add +/- 20% variation to these times even when the magnitude is the same. Figure 33 should be the worst-case overdrive scenario (Vin < -1V) so it will induce the longest response time possible (~18µs). As the overdrive gets less severe, the response time should go down.

    Sincerely,

    Peter

  • 0 in reply to Peter Iliya
    Prodigy 140 points

    Hello,
    In the case ina180 has no reference, that is, 50% of the ina180 will probably have an overload when connecting a load, I imagine it would be interesting in the future to have a maximum response time value when it has an offset of -150uv.